FIELD OF THE INVENTION
The invention pertains to an inductive rotational-speed transmitter for registering the rotational speed of a motor vehicle wheel with a hub that is rotatably mounted via the hub on an axle journal. The wheel-speed sensor comprises a transmitter wheel connected to the wheel and formed by a sequence of regions of magnetizable material that are separated from one another by regions of non-magnetizable or barely magnetizable material. A magnet is non-rotatably mounted and its magnetic flux is varied by the transmitter wheel, in dependence on the rotational speed, as the wheel rotates. The magnetic flux change is registered by a coil disposed in the vicinity of the magnet and a corresponding signal is fed to an evaluation device.
A rotational-speed transmitter of that generic type is disclosed in U.S. Pat. No. 5,291,130 to J. Kendzior, entitled "Vehicle Wheel Speed Sensor Employing an Adaptable Rotor Cap" (corresponding European publication EP 0 609 716). The prior art configuration has the disadvantage that the output signal can be very difficult to evaluate, since the sinusoidal voltage caused by the magnetic field change does not have a sufficiently large amplitude to form a signal that is capable of differentiation.